Feeding mechanism

ABSTRACT

A feeding mechanism. The feeding mechanism includes a shaft, an arm and a resilient element. The arm rotates on the shaft and has a second contact surface. The resilient element has a first contact surface contacting the second contact surface at a first contact point and exerts a first torque on the shaft when the arm is in a first position, and the first contact surface contacts the second contact surface at a second contact point, exerting a second torque on the shaft when the arm is in a second position, the first torque being substantially equal to the second torque.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates in general to a feeding mechanism, and more particularly, to a feeding mechanism capable of feeding media sheets of various thickness precisely.

2. Description of the Related Art

Referring to FIG. 1, the feeding mechanism 10 of a conventional business machine has a roller 12, a plurality of detachable separators 14, a shaft 16, an arm 18 and a resilient element 26 such as a torsion spring. The arm 18 is rotatable on the shaft 16, and the resilient element 26 exerts a spring force on the arm 18 such that the media sheets in the tray 22 can be driven by the roller 12.

The included angle between the arm 18 and the tray 22 dominates the deformation of resilient element 26. As shown in FIGS. 2 a and 3 a, when the tray 22 is empty, the deformation of resilient element 26 exceeds that when the tray 20 filled with sheets S. Referring to FIGS. 2 b and 3 b, the resilient element 26 has a deforming angle α when the tray 22 is empty and a larger deforming angle β when filled. As the resilient element 26 has a larger deforming angle when filled, a larger normal force is exerted on the sheets S. When only a few sheets S are in the tray 22, the resilient element 26 merely exerts minimal force on the arm 18, and improper feeding may occur because the arm 18 does not exert adequate normal driving force on the sheets S. On the contrary, when a large number of sheets S are loaded in the tray 22, as shown in FIG. 3 a, accidental feeding of multiple sheets may occur as the arm 18 exerts excess normal diving force thereon.

FIG. 4 illustrates sheets of various thicknesses applied in the conventional feeding mechanism 10. With respect to the thickest sheet 202, the roller 12 must apply a proper driving force, between 12˜70 g, to feed a single sheet. Misfeed (no sheet is loaded) occurs when the normal driving force is less than 12 g, and multiple feed (multiple sheets are driven at the same time) occurs when the normal driving force is over 70 g.

If the roller 12 provides a normal driving force between 10˜30 g with respect to loading a number of the sheets 202 as shown by the hatched region R in FIG. 4, the sheets 202 may be misfed when force is less than 10 g from the overlap between the hatched region A and R shown in FIG. 4. Moreover, when the thinnest sheets 210 receive normal driving force over 25 g, multiple feed may occur from the overlap between the hatched region B and R shown in FIG. 4.

As mentioned above, due to the excessively broad range of normal driving force, only sheets 204, 206, 208 can be assumed of precise delivery by the conventional feeding mechanism 10. It is therefore not convenient to apply media sheets of various thicknesses.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide a feeding mechanism applicable with sheets of various thickness. The feeding mechanism includes a shaft, an arm and a resilient element. The arm rotates on the shaft and has a second contact surface. The resilient element has a first contact surface contacting the second contact surface at a first contact point and exerts a first torque on the shaft when the arm is in a first position, and the first contact surface contacts the second contact surface at a second contact point, exerting a second torque on the shaft when the arm is in a second position, the first torque being substantially equal to the second torque.

DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings, given by way of illustration only and thus not intended to be limitative of the present invention.

FIG. 1 is a perspective diagram of a conventional feeding mechanism.

FIG. 2 a is a lateral view of the feeding mechanism when the tray is empty, based on FIG. 1.

FIG. 2 b is a perspective diagrams of the resilient element when the tray is empty, based on FIG. 2 a.

FIG. 3 a is a lateral view of the feeding mechanism when the tray is filled, based on FIG. 1.

FIG. 3 b is a perspective diagram of the resilient element when the tray is filled, based on FIG. 3 a.

FIG. 4 is a diagram of a conventional feeding mechanism applying a normal driving force with respect to sheets of various thicknesses.

FIG. 5 is a perspective diagram of the feeding mechanism in accordance with the present invention.

FIGS. 6 a, 6 b, 6 c are perspective diagrams of a resilient element exerting different spring forces on the contact portion in accordance with the present invention.

FIG. 6 d is a perspective diagram of the resilient element exerting a constant torque T on the shaft in accordance with the present invention.

FIG. 7 is a diagram illustrating the feeding mechanism applying a normal driving force with respect to sheets of various thicknesses in accordance with the present invention.

FIGS. 8 a, 8 b, 8 c are perspective diagrams of the second embodiment in accordance with the present invention.

FIGS. 9 a, 9 b, 9 c are perspective diagrams of the third embodiment in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION FIRST EMBODIMENT

An object of the present invention is to provide a feeding mechanism preventing misfeed and multiple feed. The feeding mechanism is applied to business machines, such as printers or scanners. Referring to FIG. 5, the feeding mechanism has a shaft 33, an arm 18 and a resilient element 26. The arm 18 is rotatable on the shaft 33 and has a contact portion 66. The resilient element 26 is a tension spring rotating on a pivot 51, having a fixed end 31 and an extended portion 32. The extended portion 32 has a first contact surface Ca contacting and sliding on the second contact surface Cb of the contact portion 66 at a contact point C in 3-D space.

In this embodiment, the resilient element 26 exerts a contacting force F at the contact point C and applies a torque T to the shaft 33. The torque T is determined by the contacting force F and the distance from the shaft 33 to the contact point C. To exert a constant normal driving force P on the sheets, the contact surfaces Ca and Cb are predetermined such that the resilient element 26 can apply a constant torque T to the shaft 33. As the distance from the shaft 33 to the roller 12 is fixed, a constant driving force P can be therefore applied to the sheets.

Referring to FIGS. 6 a, 6 b and 6 c, when the resilient element 26 has different deforming angles αl, α2 and α3 respectively, it exerts forces F1, F2 and F3 on the contact portion 66, wherein the arm 18 is correspondingly in the first, second and third positions. Particularly, the relationships between the resilient element 26 deforming angles and the driving forces are α1>α2>α3 and F1<F2<F3.

In FIG. 6 a, the fixed end 31 and the pivot 51 are fixed to the tray 22 as shown in FIG. 1, wherein the first contact surface Ca contacts the second contact surface Cb at a contact point C1 in 3-D space. When the sheets in the tray 22 elevate the arm 18, forming an inclined angle β1, the resilient element 26 is compressed at a deforming angle α1 and exerts a force F1 on the contact portion 66. As shown in FIG. 6 a, the force F1 applies a torque T1 to the shaft 33, wherein T1=F1·d1 (d1 is the distance from the shaft 33 to the contact point C1).

When thicker or more sheets are loaded, as shown in FIG. 6 b, the arm 18 is elevated forming an inclined angle β2, and the resilient element 26 is compressed at a deforming angle α2 and exerts a force F2 on the contact portion 66, wherein α1>α2. The force F2 applies a torque T2 to the shaft 33, wherein T2=F2 d2 (d2 is the distance from the shaft 33 to the contact point C2).

In FIG. 6 c, when the loaded sheets are thicker or more than FIG. 6 b, the arm 18 is elevated forming an inclined angle β3, and the resilient element 26 is compressed at a deforming angle α3 and exerts a force F3 on the contact portion 66, wherein α1>α2>α3. As shown in FIG. 6 c, the force F3 applies a torque T3 to the shaft 33, wherein T3=F3 d3 (d3 is the distance from the shaft 33 to the contact point C3).

With respect to the three states and diagrams mentioned, the resilient element 26 undergoes different compressing forces and has the deforming angles α1, α2 and α3 respectively, wherein α1>α2>α3. Moreover, the corresponding contacting forces F1, F2 and F3 are exerted on the contact points C1, C2 and C3 between the resilient element 26 and the contact portion 66, wherein F1<F2<F3. As the angles α1, α2, α3 and the forces F1, F2 and F3 can be detected, the first contact surface Ca and the second contact surface Cb are practically designed with respect to the corresponding distances d1, d2 and d3 to meet the condition of T=T1=F1 d1=T2=F2 d2=T3=F3 d3=Tn, wherein Tn is a constant.

Referring to FIG. 6 d, the resilient element 26 contacts the contact portion 66 and applies a constant torque T to the shaft 33. The constant torque T is transferred to the arm 18 such that the roller 12 applies a constant driving force to the sheets. As mentioned, the first and second contact surface Ca and Cb are predetermined to meet the condition of T=T1=F1 d1=T2=F2 d2=T3=F3 d3=Tn, wherein Tn is a constant.

Regardless of the contact point between the contact portion 66 and the resilient element 26, the feeding mechanism of the present invention can always apply a constant and stable torque to the arm 18 to feed smoothly without misfeed and multiple feed. It is therefore more suitable for use with sheets of various thicknesses.

FIG, 7 illustrates sheets 302, 304, 306, 308, 310 of various thicknesses applied to the feeding mechanism of the present invention. With respect to the thickest sheet 302 according to FIG. 7, when the roller 12 applies a normal driving force between 12˜70 g, the sheets are properly fed one by one. With respect to the thinnest sheet 302, when the roller 12 applies a force between 3˜25 g, the sheets are properly fed one by one. Referring to FIG. 7, the roller 12 of the present invention is capable of applying a maximum normal driving force of 20 g to the sheets when the tray 20 is filled and a minimum normal driving force of 15 g when the tray 20 is empty. Therefore, sheets 302, 304, 306, 308, 310 are all deliverable, with no threat of misfeed and multiple feed, due to the stable driving force according to the present invention.

SECOND EMBODIMENT

Referring to FIGS. 8 a, 8 b and 8 c, the resilient element 26 is connected to a contacting member 7 with the extended portion 32 fixed thereon, wherein the contacting member 7 and the extended portion 32 are rotatable on the pivot 71 fixed to the tray 22 as shown in FIG. 1. The contacting member 7 has a slot 70 with a first contact surface Ca′, wherein the second contact surface Cb is movable in the slot 70 and contacts the first contact surface Ca′. As shown in FIGS. 8 a, 8 b and 8 c, the resilient element 26 takes deforming angles α1, α2 and α3 respectively when the arm 18 is elevated when loading sheets of different thicknesses.

THIRD EMBODIMENT

Referring to FIGS. 9 a, 9 b and 9 c, the contacting member 7 is rotatable on the pivot 71 fixed to the tray 22 as shown in FIG. 1, and a spring 8 connects the contacting member 7 and the tray 22. The contacting member 7 has a slot 70 with a first contact surface Ca′, wherein the second contact surface Cb is movable in the slot 70 and contacts the first contact surface Ca′. As shown in FIGS. 9 a, 9 b and 9 c, the spring 8 extended when the arm 18 is propped up when loading different thicknesses of sheets. As mentioned, the contact surfaces Ca′ and Cb are predetermined according to the constant torque condition such that the tension spring 8 exerts a constant torque on the shaft 33 to feed the media sheets smoothly.

In summary, the present invention provides a feeding mechanism exerting a stable and constant driving force on media sheets to prevent misfeed and multiple feed. The profiles of the resilient element 26 and the arm 18 are appropriately designed to compensate for variations in spring force, and constant torque minimizes instability of the driving force applied to the sheets. That is, considering the variation of spring force from the resilient element 26, the first contact surface Ca and second contact surface Cb are therefore calculated and predetermined to exert a constant torque on the shaft 33. For arrangement in a restricted space, one contact surface (such as the first contact surface Ca) can be determined first, and the other corresponding contact surface (such as the second contact surface Cb) is determined according to the constant torque conditions mentioned, wherein the first contact surface Ca or the second contact surface Cb can be flat or curved.

While the invention has been described by way of example and in terms of the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation to encompass all such modifications and similar arrangements. 

1. A feeding mechanism, comprising: a shaft; an arm rotating on the shaft, having a second contact surface; and a resilient element having a first contact surface, wherein the first contact surface contacts the second contact surface at a first contact point and exerts a first torque on the shaft when the arm is in a first position, contacting the second contact surface at a second contact point, and exerts a second torque on the shaft when the arm is in a second position, the first torque being substantially equal to the second torque.
 2. The feeding mechanism as claimed in claim 1 further comprising a roller connected to the arm, contacting a media sheet and exerting the first torque thereon.
 3. The feeding mechanism as claimed in claim 1 further comprising a tray with at least one media sheet disposed therein.
 4. The feeding mechanism as claimed in claim 3, wherein the resilient element is fixed to the tray.
 5. The feeding mechanism as claimed in claim 1, wherein the resilient element is a torsion spring.
 6. The feeding mechanism as claimed in claim 5, wherein the torsion spring has an extended portion with the second contact surface disposed thereon.
 7. The feeding mechanism as claimed in claim 6, wherein the torsion spring has a fixed end and a pivot, both fixed to the tray, and the extended portion rotates on the pivot.
 8. The feeding mechanism as claimed in claim 1, wherein the first contact surface is a flat surface.
 9. The feeding mechanism as claimed in claim 1, wherein the second contact surface is a flat surface.
 10. A feeding mechanism, comprising: a shaft; an arm rotating on the shaft, having a second contact surface; a resilient element; and a contacting member connecting the resilient element and having a first contact surface, wherein the first contact surface contacts the second contact surface at a first contact point and exerts a first torque on the shaft when the arm is in a first position, contacting the second contact surface at a second contact point, and exerts a second torque on the shaft when the arm is in a second position, the first torque being substantially equal to the second torque.
 11. The feeding mechanism as claimed in claim 10 further comprising a roller connected to the arm, wherein the roller contacts a media sheet and exerts the first torque thereon.
 12. The feeding mechanism as claimed in claim 10 further comprising a tray with at least one media sheet disposed therein.
 13. The feeding mechanism as claimed in claim 10, wherein the resilient element is a torsion spring.
 14. The feeding mechanism as claimed in claim 13, wherein the torsion spring is fixed to the tray.
 15. The feeding mechanism as claimed in claim 14, wherein the torsion spring has a fixed end and a pivot both fixed to the tray, and the extended portion rotates on the pivot.
 16. The feeding mechanism as claimed in claim 12, wherein the resilient element is a tension spring connecting the tray and the contacting member.
 17. The feeding mechanism as claimed in claim 10, wherein the first contact surface is a flat surface.
 18. The feeding mechanism as claimed in claim 10, wherein the second contact surface is a flat surface. 